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1.
煤层瓦斯渗透率是影响瓦斯抽采和动力灾害防治的重要参数。为了研究煤体损伤和剪胀变形对渗透率的影响,首先引入损伤变量反映煤体损伤破坏状态,建立了基于体应变增量的煤体损伤本构模型。并采用Hurst指数表征裂隙表面粗糙度,基于裂隙表面的分形特征,建立了裂隙渗透率在压缩和剪切作用下的演化模型。通过对TOUGH2和FLAC3D软件进行二次开发,建立了基于双重孔隙模型的TOUGH2(CH4)-FLAC气-固耦合数值分析工具。采用本软件对煤样单轴压缩过程进行模拟分析,结果表明：煤体的破坏是损伤单元累积和贯通的结果,最终形成贯通煤体的损伤带是造成煤体失稳破坏的主因;围岩内的渗透率增加区域与损伤区位置基本一致,其中裂隙系统的渗透率增加幅度最大可达2个数量级;剪切破坏区的裂隙发生剪胀变形,引起裂隙渗透率大幅增加。建立的理论模型与数值计算工具为制定瓦斯治理措施提供了理论指导。 相似文献
2.
为了研究深部煤体在开采扰动影响下的渗透率演化规律,以三向应力条件下的煤体渗透率模型为基础,从吸附解吸作用引起裂隙变形和损伤破裂造成煤基质弹性模量劣化的角度进行理论推导,引入内膨胀应变系数的概念,同时基于Drucker-Prager破坏准则的损伤本构关系建立了两种考虑煤体损伤破裂的渗透率演化模型——指数型和立方型,并且对常规三轴加载、开采扰动加卸载和改变气体压力下的瓦斯渗透试验结果进行了拟合分析。结果表明：所构建的两种模型可以较好地反映常规三轴加载和开采扰动加卸载下煤体渗透率的分区段变化特征,也可以描述有效围压恒定条件下煤体渗透率随气体压力升高而降低的规律。在开采扰动加卸载和改变气体压力的试验中,指数型的拟合效果略优于立方型。研究结果可为深部煤炭开采及瓦斯抽采的工作提供指导。 相似文献
3.
《岩土力学》2019,(11):4289-4298
为了探究采掘扰动和温度变化对工作面前方煤体渗透率的影响,将引起煤体裂隙变形的因素划分为有效应力、吸附解吸和热膨胀3部分。基于损伤力学、吸附理论和热应力理论推导出了采掘扰动与温度耦合作用下煤体裂隙应变表达式,进而构建了采掘扰动与温度耦合影响下工作面前方煤体渗透率模型。结合改变温度、同时改变扰动应力和温度的两种渗透率试验结果对所建立的模型适用性进行了拟合分析,并对模型中的参数敏感性进行了讨论。结果表明:所构建的煤体渗透率模型可以较好地描述采掘扰动与温度耦合影响下煤体渗透率的演化过程;在同一温度下,煤体渗透率随着内膨胀应变系数的增大而增大,随着热内膨胀应变系数的增大而减小。研究结果可为煤炭开采及瓦斯抽采的工作提供指导。 相似文献
4.
构造煤渗透率对温度变化响应规律的试验研究 总被引：1，自引：0，他引：1
针对含瓦斯构造煤渗透率与温度变化关系,利用自主研发的含瓦斯煤岩热-流-固耦合三轴渗流试验装置,开展不同应力条件下含瓦斯构造煤原煤样的渗透率与温度变化的试验研究。试验结果表明：（1）在试验温度变化过程中,构造煤样渗透率随温度升高而降低,渗透率与温度变化呈现负指数函数分布规律;（2）在试验温度变化过程中,构造煤渗透率损失率与有效应力符合Boltzmann分布,渗透率损失率存在有效应力门槛值大约为4.515 MPa。渗透率变化主要分为渗透率加速变化与平稳变化两个阶段,构造煤样渗透率从加速阶段过渡到平稳变化温度大约为45 ℃;（3）在温度21～80 ℃范围内,渗透率敏感性系数数量级为10-2,温度变化对构造煤样渗透率影响不显著。同时,有效应力的增加使得温度敏感性系数降低。 相似文献
5.
气固耦合作用下温度对煤瓦斯渗透率影响规律的实验研究 总被引：5，自引：1，他引：4
为得到温度对煤瓦斯渗透率的影响规律, 在实验室通过改装三轴渗透仪, 进行了不同温度条件下煤瓦斯的渗透率测定实验。实验结果表明, 在不同温度下, 渗透率随有效应力的减小均呈二次抛物线趋势, 即渗透率先减小后增大。在卸载初期, 温度较低时煤瓦斯渗透率下降梯度比高温时大, 渗透率值较高; 卸载后期, 较高温度时煤瓦斯渗透率上升梯度比低温时大, 渗透率值大。由实验可知, 煤层气开采过程中, 对于不同温度, 煤瓦斯渗透率的变化关系均具有典型煤层气开采的三阶段主导作用特征。有效应力、气体吸热和煤固体受热是影响煤体渗透率的重要因素。在卸载初期, 煤固体受热膨胀及有效应力对渗透率起主导作用, 卸载中后期, 气体滑脱和气体吸热对渗透率起主导作用。实验分析后认为, 开采煤层气时采用先压裂后注热的方式将有助于提高煤层气的产量。 相似文献
6.
为了探究有效应力对高煤级煤储层渗透率的控制作用及其应力敏感性的各向异性,对5块高煤级煤样进行了覆压孔渗实验,揭示了有效应力对煤储层渗透率的控制机理。以3.5 MPa模拟原始地层压力发现,煤岩在平行主裂隙和层理面方向具有最高的初始渗透率,垂直层理面方向初始渗透率最低;有效应力从3.5 MPa增加到15.5 MPa的过程中,渗透率呈现出良好的幂函数降低趋势;渗透率伤害/损失的各向异性表明平行主裂隙方向渗透率伤害率和损失率最大,且不同方向应力敏感性受裂隙的宽度及其展布方向的控制;裂隙压缩系数随应力的增加呈现降低趋势,但由于高煤级煤岩压缩难度大,裂隙压缩系数的各向异性不明显。有效应力对渗透率控制的实质为通过减小煤储层孔裂隙体积降低渗透率,从而对各个方向上的渗透率均造成较大的不可逆伤害。 相似文献
7.
为探究煤岩在变轴压加载下的变形破坏和瓦斯渗流演化规律,以原煤煤粉压制的煤体试件为研究对象,采用含瓦斯煤热流固耦合三轴伺服渗流试验系统,进行了5种不同轴压加载路径下的煤体三轴压缩及瓦斯渗流试验。研究结果表明,煤体变形可分为压密、稳定发展、非稳定破裂发展和破裂后4个阶段;压密阶段试件的应变变化速率主要与张开性结构面和裂隙有关,与轴压加载区间无关,稳定发展阶段虽然轴压加载速率不同,但在相同的轴压加载区间,轴向应变变化速率基本相同;变轴压加载前期煤体渗透率与轴压的加载速率呈负相关变化,中后期渗透率变化速率与轴压加载速率相关性不大。研究结论对指导冲击地压以及煤与瓦斯突出的监测预警有着重要意义。 相似文献
8.
煤层具有强波阻抗差、低阻抗的特性,对地震勘探来说是一种典型的薄层。因为其黏弹性和速度各向异性导致薄层反射波场异常,为了定量分析黏弹性和速度各向异性对薄层地震反射的影响,针对强波阻抗差薄层模型,基于波动方程数值模拟方法,正演得到弹性速度各向同性、黏弹性速度各向同性及黏弹性速度各向异性的地震波场,并对比分析了3种模型的弹性波地震反射特征。研究结果表明:黏弹性对薄层的反射产生不可忽略的影响,会明显降低薄层弹性波的反射振幅,但黏弹性速度各向同性与各向异性对薄层的弹性波反射影响差异不大。相比于弹性各向同性情况,黏弹性会引起反射纵波（PP波）瞬时频率最大可达8%的改变量,而对转换横波（PS波）仅有3%的改变量,可以忽略不计。上述研究为利用构造煤品质因子极低的特征来预测构造煤提供了可能。 相似文献
9.
开采扰动诱发的煤与瓦斯突出是煤矿生产过程中的主要瓦斯动力灾害之一。为系统探索开采扰动下煤体损伤演化特征和瓦斯渗流规律,拟开展不同瓦斯压力下全应力应变–渗流实验。通过考虑气体吸附和热膨胀效应修正广义胡克定律,建立基于塑性变形的煤体损伤本构关系,进一步构建考虑损伤的分段渗透率模型。结果表明:以渗透率突变点为界,可将煤体渗透率分为峰前和峰后2个变化阶段。其中,峰前呈指数型降低,而峰后急剧增加,峰值抗压强度和弹性模量均随着瓦斯压力升高而降低;煤体轴向塑性应变和损伤演化规律具有良好的一致性,二者均呈现出峰前变化不大,峰后激增的变化趋势;利用不同瓦斯压力和50℃实验数据对所建的损伤模型及渗透率模型进行验证,得到理论曲线和实验数据具有较好的吻合度,表明新建模型可较好地反映不同条件下煤体破坏失稳过程中的损伤演化规律和瓦斯渗流特征。 相似文献
10.
转向压裂是一项新兴的水力压裂技术,在平面渗透率各向异性储层中转向垂直裂缝具有更好的增产效果.基于渗流力学之汇源叠加理论,建立了平面渗透率各向异性储层中转向垂直裂缝的增产评价解析模型,并给出了计算对比和应用算例.分析结果表明:裂缝与渗透率主轴间的夹角（裂缝斜角）微弱影响均匀各向同性储层中井的产能,但明显影响均匀各向异性储层中井的产能;裂缝斜角变化导致沿优势渗透率方向有效流入面积变化,有效流入面积越大,无量纲生产指数越大,产能亦高.因此建议选择平面方向渗透率差异较大的储层进行转向压裂,以期获得更好的经济效益. 相似文献
11.
In order to investigate the effect of material anisotropy on convective instability of three-dimensional fluid-saturated faults, an exact analytical solution for the critical Rayleigh number of three-dimensional convective flow has been obtained. Using this critical Rayleigh number, effects of different permeability ratios and thermal conductivity ratios on convective instability of a vertically oriented three-dimensional fault have been examined in detail. It has been recognized that (1) if the fault material is isotropic in the horizontal direction, the horizontal to vertical permeability ratio has a significant effect on the critical Rayleigh number of the three-dimensional fault system, but the horizontal to vertical thermal conductivity ratio has little influence on the convective instability of the system, and (2) if the fault material is isotropic in the fault plane, the thermal conductivity ratio of the fault normal to plane has a considerable effect on the critical Rayleigh number of the three-dimensional fault system, but the effect of the permeability ratio of the fault normal to plane on the critical Rayleigh number of three-dimensional convective flow is negligible. 相似文献
12.
Coal swelling/shrinkage during gas adsorption/desorption is a well-known phenomenon. For some coals the swelling/shrinkage shows strong anisotropy, with more swelling in the direction perpendicular to the bedding than that parallel to the bedding. Experimental measurements performed in this work on an Australian coal found strong anisotropic swelling behaviour in gases including nitrogen, methane and carbon dioxide, with swelling in the direction perpendicular to the bedding almost double that parallel to the bedding. It is proposed here that this anisotropy is caused by anisotropy in the coal's mechanical properties and matrix structure. The Pan and Connell coal swelling model, which applies an energy balance approach where the surface energy change caused by adsorption is equal to the elastic energy change of the coal solid, is further developed to describe the anisotropic swelling behaviour incorporating coal property and structure anisotropy. The developed anisotropic swelling model is able to accurately describe the experimental data mentioned above, with one set of parameters to describe the coal's properties and matrix structure and three gas adsorption isotherms. This developed model is also applied to describe anisotropic swelling measurements from the literature where the model was found to provide excellent agreement with the measurement. The anisotropic coal swelling model is also applied to an anisotropic permeability model to describe permeability behaviour for primary and enhanced coalbed methane recovery. It was found that the permeability calculation applying anisotropic coal swelling differs significantly to the permeability calculated using isotropic volumetric coal swelling strain. This demonstrates that for coals with strong anisotropic swelling, anisotropic swelling and permeability models should be applied to more accurately describe coal permeability behaviour for both primary and enhanced coalbed methane recovery processes. 相似文献
13.
为研究原状马兰黄土的渗透各向异性,以延安削山造地重大工程开挖所揭露的完整黄土剖面中的马兰黄土层为研究对象,采用室内变水头渗透试验获取不同埋深不同渗流时长原状黄土垂直向和水平向的渗透系数,并对试验前后黄土试样垂直向和水平向SEM（scanning electron microscope）电镜扫描结果进行分析,从微观结构上揭示原状马兰黄土结构各向异性的原因。结果表明：原状黄土垂直向和水平向饱和渗透系数具有显著各向异性,且垂直向和水平向渗透系数都随渗流时间的持续而减小,各向异性渗透性能在时间尺度上具有某种衰减关系;同时,原状黄土各向异渗透性能随埋深的增大而逐渐减弱;土颗粒结构的接触、排列方式是导致黄土原生各向异性的根本原因,也是导致渗流初始阶段渗透系数各向异性的原因,而渗流作用产生的次生结构各向异性则使渗透系数各向异性在时间尺度上表现得更为明显。 相似文献
14.
由于地质成因的不同,岩石渗透率往往具有不同程度的大小和方向性差异,即呈各向异性的特点。目前,岩石渗透率方向性特征的理论和试验研究仍然不足,缺乏岩石渗透率各向异性量化评估。基于国内CCUS场地储层砂岩,沿正交方向钻取岩芯试件若干,完成瞬态法覆压渗透率测试。试验结果表明,特低渗砂岩正交方向渗透率随围压（上覆岩层压力）加载呈幂律函数递减,当围压加载至20 MPa以后,正交方向渗透率差异性逐步降低,即渗透率由各向异性逐步向各向同性过渡,且储层砂岩竖向渗透率压力敏感系数普遍低于水平侧向。通过建立一种空间坐标系下渗透率计算模型,将岩石内部渗流规律等效为空间正交方向渗透率模型,并借用统计学标准差定义提出渗透率各向异性系数?k,将不同岩性储层岩石渗透率不均匀性作归一化处理,定量地描述了覆压试验过程中试件渗透率各向异性的变化规律。 相似文献
15.
An anisotropic geomechanical model for jointed rock mass is presented. Simultaneously with deriving the orthotropic anisotropy elastic parameters along the positive axis, the equivalent compliance matrix for the deflection axis orthotropic anisotropy was derived through a three-dimensional coordinate transformation. In addition, Singh’s analysis of the stress concentration effects of intermittent joints was adopted, based on two groups of intermittent joints and a set of cross-cutting joints in the jointed rock mass. The stress concentration effects caused by intermittent joints and the coupling effect of cross-cutting joints along the deflection-axis are also considered. The proposed anisotropic mechanics parameters method is applied to determine the deformation parameters of jointed granite at the Taishan Nuclear Power Station. Combined with the deterministic mechanical parameters of rock blocks and joints, the deformation parameters and their variability in jointed rock masses are estimated quantitatively. The computed results show that jointed granite at the Taishan Nuclear Power Station exhibits typical anisotropic mechanical characteristics; the elastic moduli in the two horizontal directions were similar, but the elastic modulus in the vertical direction was much greater. Jointed rock elastic moduli in the two horizontal and vertical directions were respectively about 24% and 37% of the core of rock, showing weakly orthotropic anisotropy; the ratio of elastic moduli in the vertical and horizontal directions was 1.53, clearly indicating the transversely isotropic rock mass mechanical characteristics. The method can be popularized to solve other rock mechanics problems in nuclear power engineering. 相似文献
16.
晚更新世黄土渗透性的各向异性及其机制研究 总被引：3，自引：0，他引：3
非饱和黄土的渗透性是非饱和黄土性质的重要组成部分。研究黄土不同方向的渗透性对确定其湿陷范围和由于水的渗透引起的黄土滑坡具有很重要的理论意义。研究了黄土渗透性的各向异性特征及其机制。以具有明显各向异性的西安Q3原状黄土为研究对象,用TEN型张力计测量了黄土试样不同方向的、不同含水率下的吸力;用变水头渗透试验测量了黄土竖直和水平方向的饱和渗透系数。结果表明,当体积含水率在23%～41%时,张力计沿不同方向插入土样所测吸力相差不大;竖直方向的饱和渗透系数是水平方向的4.02倍。在吸力测量的基础上,根据土-水特征曲线,确定了竖直和水平方向的非饱和黄土的渗透系数。得出在黄土不同方向,随着吸力的增大或减小,渗透系数减小或增大;竖直方向的渗透系数普遍地大于水平方向的渗透系数;当吸力小于57 kPa时,随着吸力的增大,竖向渗透系数与水平向渗透系数的差值减小。通过观测黄土的结构,得出黄土结构对其渗透性有重要影响。 相似文献
17.
Egor V. Dontsov 《国际地质力学数值与分析法杂志》2019,43(2):519-529
This study investigates parametric space of solutions for a planar hydraulic fracture propagating in a homogeneous anisotropic rock. It is assumed that the fracture has an elliptical shape and is driven by a power-law fluid. The purpose of this study is to investigate the influence of anisotropy and power-law fluid rheology on the parametric space of solutions. Rock anisotropy is represented by having two values of fracture toughness, one in the vertical direction and another one in the horizontal direction. Similarly, the effect of elastic anisotropy is approximated by using two different effective elastic moduli in the vertical and horizontal directions. In contrast to the isotropic case, for which there are four limiting solutions, the problem for anisotropic rocks features six different limiting cases. These cases represent competition between toughness and viscosity in the vertical and horizontal directions and competition between fluid storage inside the fracture and fluid leak-off into formation. Approximate expressions for the limiting solutions are obtained using global volume balance and tip asymptotic solutions. Despite the developed solutions rely on a series of approximations, they precisely capture all the scaling laws associated with the problem. Zones of applicability of these limiting solutions are calculated, and their dependence on the problem parameters is investigated. 相似文献
18.
武汉地区长江Ⅰ级阶地含水层在水流等沉积动力的分选作用和上覆土层压力的固结作用下,其渗透系数必然存在各向异性。因此,基于含水层渗透系数的各向同性和以单井稳定流抽水试验得到的含水层水文地质参数所完成的基坑降水设计亦必然与工程实际存在差异。通过现场分层抽水试验、群井抽水试验,结合三维数值模拟反演计算,得出了武汉长江Ⅰ级阶地各含水层水文地质参数的基本规律和特性,即：各含水层渗透系数自上而下逐渐增加且表现为各向异性,其水平渗透系数大于垂直渗透系数,其比值介于1.6～2.6之间。工程实例表明,采用各向异性的水文地质参数和三维渗流分析进行的超深基坑降水设计,结果更接近于实际,且有利于降低工程造价和基坑周边环境损伤,亦有利于节约宝贵的地下水资源。 相似文献
19.
Existing solutions to Mandel's problem focus on isotropic, transversely isotropic, and orthotropic materials, the last two of which have one of the material symmetry axes coincide with the vertical loading direction. The classical plane strain condition holds for all these cases. In this work, analytical solution to Mandel's problem with the most general matrix anisotropy is presented. This newly derived analytical solution for fully anisotropic materials has all the three nonzero shear strains. Warping occurs in the cross sections, and a generalized plane strain condition is fulfilled. This solution can be applied to transversely isotropic and orthotropic materials whose material symmetry axes are not aligned with the vertical loading direction. It is the first analytical poroelastic solution considering mechanical general anisotropy of elasticity. The solution captures the effects of material anisotropy and the deviation of the material symmetry axes from the vertical loading direction on the responses of pore pressure, stress, strain, and displacement. It can be used to match, calibrate, and simulate experimental results to estimate anisotropic poromechanical parameters. This generalized solution is capable of reproducing the existing solutions as special cases. As an application, the solution is used to study the responses of transversely isotropic and orthotropic materials whose symmetry axes are not aligned with the vertical loading direction. Examples on anisotropic shale rocks show that the effects of material anisotropy are significant. Mandel-Cryer's effects are highly impacted by the degree of material anisotropy and the deviation of the material symmetry axes from the vertical loading direction. 相似文献
20.
基于提出的横观各向同性饱和多孔介质Biot波动方程的一般解,研究了饱和半空间地基在竖向点源简谐激振荷载作用下地表振动的衰减特征,分析了激振频率以及横观各向同性饱和土介质的各向异性参数和孔隙渗透系数对地表振动特征的影响。计算结果表明,低频和高频激振时,地表位移衰减特性存在明显差异;在饱和土的各向异性参数中,纵向和水平方向动态渗透系数比值和刚度系数比值对地表位移衰减影响最大,这也说明采用各向同性饱和介质的动力学模型不能准确地描述具有明显各向异性特性的饱和土地基的动力特性。 相似文献